1. Field of the Invention
The present invention relates to liquid crystal display (LCD) devices, and more particularly, to a method of fabricating liquid crystal panels having an improved picture quality.
2. Discussion of the Related Art
Recently, liquid crystal display (LCD) devices have attracted attention as substitutes for cathode ray tubes (CRTs). LCDs have the advantages of being thin, lightweight, and portable, and consume little power. In particular, being lightweight is highly important in many applications.
An LCD device is typically comprised of two glass substrates and a liquid crystal layer that is disposed between the two glass substrates. To reduce the weight of an LCD device it is beneficial to use thin glass substrates. This is particularly important because the glass substrates are typically the heaviest part of an LCD device. Thus, thin glass substrates are beneficial. However, because of manufacturing stresses it is better to use relatively thick glass substrates during fabrication. In practice, LCD devices are often fabricated using thick glass substrates that are subsequently thinned. There are two basic methods of thinning glass substrates, polishing and etching. The principles of the present invention are primarily directed to etched glass substrates.
The accompanying drawings illustrate a related art method of fabricating LCD devices. FIG. 1 shows a block diagram of related art fabricating processes, FIG. 2 shows a device for etching substrates, and FIG. 3 helps explain problems that can occur in the related art method.
Referring now to FIG. 1, a plurality of crossing gate and data lines are formed on a first substrate, thereby defining a plurality of pixels, and then a plurality of thin film transistors (TFTs) are formed near the crossing points (S1). A passivation layer having a predetermined thickness is then formed over the first substrate, including over the TFTs (S2). The passivation layer is typically an organic insulating material comprised of BCB or acryl resin. That organic insulating material is usually applied as a liquid having a solvent that suspends the organic insulating material. After being applied, the passivation layer is heated to remove the solvent, which leaves as a vapor.
Subsequently, ITO pixel electrodes are formed on the hardened passivation layer and in electrical contact with the TFT (S3). A seal having an injection hole is then formed around the periphery of the first substrate, spacers are dispersed on a second substrate having a color filter layer, and the first and second substrates are attached to each other (S4). Attaching is typically accomplished using pressure and heat or light to harden the seal.
A liquid crystal is then injected between the first and second substrates through the injection hole in the seal, and then the injection hole is sealed to prevent liquid crystal outflow (S5).
After liquid crystal injection, the outer surfaces of the substrates are etched to reduce weight (S6). FIG. 2 shows a suitable etching device. As shown, a container 141 is filled with HF (hydrofluoric acid) 144 from an etchant supply 143. A liquid crystal display panel 145 is then dipped into the HF 144, which etches the surfaces of the liquid crystal display panel 145 formed by the first and second substrates 1 and 11 (see FIG. 3). In practice, a cassette 146 in the container 141 holds the liquid crystal display panel 145.
After etching, the liquid crystal display panel 145 is cleaned to remove the HF and is then drying. This completes a reduced weight liquid crystal display panel 145.
While generally successful, the related art liquid crystal display panel 145 has problems. The organic insulating layer is hardened by heating, which drives the solvent off as vapor fumes. Those fumes can cause contaminates 6 on the exposed surfaces of the substrates. Those contaminates are not easily removed, and any residual contaminates 6 cause uneven etching of the glass substrates. Uneven etching is a particular problem on the first substrate because the uneven etching can result in significant picture quality deterioration.
Therefore, a method of removing fume-induced contaminates from the liquid crystal display panel substrates would be beneficial. Even more beneficial would be a method of improving picture quality by planarizing the etched surfaces of the liquid crystal display panel substrates.